The manufacture of high quality leather goods results in an almost equal weight of solid waste material. The U.S. leather industry generates more than 50,000 metric tons of chrome-tanned trimmings, shavings and buffing dust each year, while the world-wide total is about ten times as much (Brown, E. M., et al., JALCA, 91: 270-276 (1996)). Animal by-products, such as trimmings and shavings from the leather industry and feathers from the poultry industry, have traditionally been disposed in landfills. However, increasing environmental concerns and escalating landfill costs necessitate that uses be found for these protein-containing by-products. This invention relates to the use of transglutaminase to produce useful products from such animal by-products. The method of producing such useful products involves incubating animal by-products in a transglutaminase-containing solution to produce transglutaminase-treated animal by-products, compressing the transglutaminase-treated animal by-products to produced a compressed product, and drying the compressed product. The transglutaminase-containing solution need not contain casein. The resulting product is stronger in comparison to controls as measured by force in compression.
The use of transglutaminase to cross-link a variety of proteins, resulting in products with unique properties and improved functionality, has been widely described in the literature. For example, transglutaminase has been used to improve the functional properties of food proteins such as wheat gluten and milk proteins (Chobert, J. M., et al., Nahrung, 40 (4): 177-182 (1996). Microbial transglutaminase treated caseinate has been used to produce larger pieces of restructured meat from their smaller pieces (Motoki, M., and K. Seguro, Trends in Food Science & Technology, 9(5): 204-210 (1998)). U.S. Pat. No. 5,531,795 described the use of microbial transglutaminase in conjunction with casein (which has long been used as a finishing agent for leather) in the area of leather finishing where transglutaminase-improved casein finishes are applied to leather; this patent is actually describing the enhancement of casein finishes with transglutaminase and then the application of these products to leather, not the binding of the finishes to leather or the binding of leather to leather.